Java Classes Generator

This code generator produces the Java domain model, i.e. the set of Java classes that represent the entities and relationships of a Structural model.

Let’s generate the code for the Java domain model of our Structural model example structural model example. You should create a JavaGenerator object, provide the Structural model, and use the generate method as follows:

from besser.generators.java_classes import JavaGenerator

generator: JavaGenerator = JavaGenerator(model=library_model)
generator.generate()

The generator writes one file per type: a <ClassName>.java for every class in the model and a <EnumName>.java for every enumeration, all in the <<current_directory>>/output folder. By default no package declaration is emitted; the classes look as follows.

Note

The three listings below are checked-in fixtures that predate the current template: they still carry a package tests.structural.library.output.java; line and a leading comment that the generator no longer emits. Read them for the class/field/method shape, not for the file header.

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// This is a template example to list the name of the classes
package tests.structural.library.output.java;
import java.util.List;
import java.util.ArrayList;

public class Author {
    private String name;
    private String email;

    public Author (String name, String email) {
        this.name = name;
        this.email = email;
    }



    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return this.email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

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// This is a template example to list the name of the classes
package tests.structural.library.output.java;
import java.time.LocalDate;
import java.util.List;
import java.util.ArrayList;

public class Book {
    private int pages;
    private LocalDate release;
    private String title;
    private List<Author> authors;
              

    public Book (int pages, LocalDate release, String title) {
        this.pages = pages;
        this.release = release;
        this.title = title;
        this.authors = new ArrayList<>();
    }

    public Book (int pages, LocalDate release, String title, ArrayList<Author> authors) {
        this.pages = pages;
        this.release = release;
        this.title = title;
        this.authors = authors;
    }

    public int getPages() {
        return this.pages;
    }

    public void setPages(int pages) {
        this.pages = pages;
    }

    public LocalDate getRelease() {
        return this.release;
    }

    public void setRelease(LocalDate release) {
        this.release = release;
    }

    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public List<Author> getAuthors() {
        return this.authors;
    }

    public void addAuthor(Author author) {
        authors.add(author);
    }
}

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// This is a template example to list the name of the classes
package tests.structural.library.output.java;
import java.util.List;
import java.util.ArrayList;

public class Library {
    private String name;
    private String address;
    private List<Book> books;
  

    public Library (String name, String address) {
        this.name = name;
        this.address = address;
        this.books = new ArrayList<>();
    }

    public Library (String name, String address, ArrayList<Book> books) {
        this.name = name;
        this.address = address;
        this.books = books;
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddress() {
        return this.address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public List<Book> getBooks() {
        return this.books;
    }

    public void addBook(Book book) {
        books.add(book);
    }
}

To emit a package declaration, pass the package_name parameter. It is independent of output_dir: the output directory decides where the files are written, package_name decides what the classes declare.

from besser.generators.java_classes import JavaGenerator

generator: JavaGenerator = JavaGenerator(
    model=library_model,
    output_dir="my_java_project",
    package_name="com.example.library",
)
generator.generate()

Will result in the following line being added to the beginning of every generated class and enum:

package com.example.library;

Parameters

  • model: The input B-UML structural model (required).

  • output_dir: Output directory (optional, default: output/ in the current directory).

  • package_name: Java package declared at the top of every generated file (optional). When omitted, no package line is emitted.